Venting members for core boxes and other moulds



Sept. 22, 1910 L Y 3,529,656

VENTING MEMBERS FOR CORE BOXES AND OTHER MOULD'S Filed Feb. 27, 1968 wmaam 1 M277 [Evy United States Patent U.S. Cl. 164-234 3 Claims ABSTRACT OF THE DISCLOSURE A venting member for mounting in a circular aperture in the wall of a mould to be invested with sand or other moulding material, comprises a circular block with fiat end faces normal to its axis and alternate arcuate peripheral recesses and projections; the projections may be of progressively decreasing radius with interrupted screw threads on their peripheries; the bases of the recesses may be inclined the axis with slots extending outwards to the bases and opening to the end faces.

This invention concerns venting members for core boxes and other moulds, the venting members being of the kind which are inserted in the walls of core boxes, patterns and other moulds to be invested with sand or other moulding material which is required to make close contact with the walls. Hereinafter the venting members will be referred to merely as vents. If pockets of air are trapped between the moulding material and the walls, they give rise to faulty cores and moulds and to faulty castings made therefrom. Vents are incorporated in a wall at appropriate positions to prevent the escape of any substantial amount of the moulding material while permitting the escape of air which would otherwise be trapped.

A known form of vent is a short tube having at that end which is at the working face of the wall of a mould a grid in the form of a mesh or of transverse slits in the otherwise closed end of the tube. Such a vent has an uneconomically short working life for several reasons. It tends to become blocked with the moulding material,

which may be hardened during heat treatment of the mould, the vent becoming progressively difficult to clean except by methods which are too harsh in that they tend to damage the vent. The vents are usually a driven fit in the mould, requiring to be knocked out with the risk of damaging the vents and/or the moulds. The grids, particularly when of wire mesh, tend to become damaged by the pressure of the moulding material during the moulding operation.

An object of the invention is to provide a robust vent which is adapted to be more readily cleaned than the known vents.

In accordance with the invention, a vent for mounting in the wall of a core box or other mould comprises a circular block bounded by two flat faces, a front face and a back face, and having circumferentially spaced arcuate recesses in the peripheral region of the block, the recesses each opening to the front and back faces and providing, between each two adjacent recesses, an arcuate projection.

Preferably the central part of the radially inner surface of each recess has at least a portion thereof which meets the back face inclined away from the axis of the block towards the front face.

When the improved vent is positioned as a close fit in a round hole in the wall of the mould, with the front face substantially flush with the working surface of the wall, the arcuate recesses provide air-escape passages; in the above mentioned preferred form, the transverse dimensions of the passages increase outwardly due to the in- 3,529,656 Patented Sept. 22, 1970 "ice clination to the axis of at least the rear parts of the radially inner surfaces of the recesses.

The outer surfaces of the projections may have a radius which progressively decreases from the front to the back of the block.

The outer surfaces of the projections may be formed with portions of a screw thread which is interrupted by the recesses.

The projections may be in the form of the lands of a screw-threading tap.

From the radially inner surface of each recess there may be at least one slot extending towards the central region of the block and between the front and back faces thereof.

Where more than one slot extends from the inner face of a recess, the slots may be mutually parallel.

The slot or one of the parallel slots extending from the inner face of a recess may extend radially relative to the axis of the. block.

Alternatively the slot, or some or all of the slots may be inclined to the radial.

The block may have at its front a formation engageable by a tool for inserting the block into a mould wall. For instance, such formation may be a projection for engagement by a box spanner, or a recess or slot for engagement by an Allen or other key or a screw driver.

A vent constructed in accordance with the invention will now be described by way of example and with reference to the accompanying diagrammatic drawing wherein:

FIG. 1 is a view looking directly at the front face of the block;

FIG. 2 is a view looking directly at the back face of theblock;

FIG. 3 is a side elevation as seen in the direction of the arrow MI in FIG. 1; and

FIG. 4 is a cross section on the line IVlV in 1.

The illustrated vent comprises a generally circular block bounded by a front face 1 and back face 2, the faces being normal to the axis of the block. In the peripheral region of the block are four uniformly dimensioned equidistantly spaced arcuate recesses 3 providing between them four uniformly dimensioned equi-distantly spaced arcuate projections 4. As represented in FIG. 1, at the front face 1 each arcuate recess 3 has a radial dimension which is less than any arcnately measured dimension of the recess. The outer faces 5 of the projections 4 have a radial dimension which progressively decreases from the front face 1 to the back face 2 so that they lie on the frustum of a cone of small taper. The outer faces 5 also have self-cutting screw thread formations so that the block as to described represents a section of a tap of which the projections 4 are the lands.

The central part of the radially inner surface of each recess 3 is machined away or otherwise formed (e.g. by casting the vent) to provide initially a flat surface, indicated by the lines 6, 6 in FIG. 4, which is inclined towards the axis of the block from a radially outer position, near the front face 1, to the back face 2. From each inclined face so formed there extend inwards three parallel slots 7, which also extend to the front and back faces 1, 2 and have their inner boundaries 8, 8 (FIG. 4) parallel to the axis of the block. It will be seen that each group of three parallel slots 7 defines a pair of interslot parallel-sided ribs 9, 9, which are also tapered at those of their surfaces which are parts of the initially flat surfaces 6, 6 inclined towards the axis of the block as above described. Instead of being flat, the inclined surfaces 6, 6 may be formed as shallow concavities as indicated by broken line 6a, 6a in FIG. 4.

Centrally on the front face 1 is a hexagonal section boss 10 adapted to be engaged by a box spanner.

The mould with which the above described vent is to be used may be of metal, for instance aluminium, which is softer than the material of which the vent is made, for instance steel with at least the self-tapping thread surfaces specially hardened. An appropriately dimensioned round hole is provided in the mould Wall and the vent is screwed in, from the working face, by means of a box spanner applied to the projection 10, cutting its own thread in the surface of the hole. The initially arcuate recesses 3 provide passages for the escape of air during investing of the mould, the passages having outwardly divergent transverse sections resulting from the inclined surfaces (6 in FIG. 4). Further air escape passages are provided by the slots 7, while at least at the working face the inter-slot ribs 9 provide a barrier and/ or support for the sand or other mould investing material.

Instead of the boss 10, there may be a non-circular recess, in the front face 1, to receive a correspondingly shaped tool such as an Allen key. Alternatively the front face 1 may be formed with a transverse slot to receive a conventional screw driver.

The size of the vent, the number of recesses 3 and projections 4 and the number of slots 7, as of course the number of vents used in a mould, will be determined by such conditions as the size and shape of the mould, the nature of the moulding material and the conditions under which the mould is to be made and perhaps heat treated.

In some cases it may be convenient to provide the mould with pre-tapped vent-receiving holes, in which case the outer surfaces 5 of the projections 4 may be portions of a right cylindrical threaded surface.

In another arrangement the surfaces 5 of the projections 4 and the surfaces of the vent-receiving holes may be plain, the vents being a push or drive fit in the holes.

In some circumstances the slots 7 may not be present and even the inner surfaces of the recesses 3 may be left plainly arcuate, that is not inclined as represented at 6 in FIG. 4.

Although described as being of metal, the material of the vent can be chosen in accordance with the circumstances under which it is to be used; for instance it may be of non-metallic plastics.

The improved vent is robust so as not to be weakened by the moulding pressures, it can be inserted in and removed from a mould quickly by facile operations, it lends itself to easy cleaning and can be entirely salvaged for re-use at least an economical number of times.

Iclaim:

1. A venting member for mounting in a circular aperture in the wall of a box to be invested with moulding material, the venting member being a circular block bounded by a front fiat face and a back fiat face, which faces are normal to the axis of the circular block, the periphery of the circular block being interrupted by circumferentially and uniformly spaced recesses defining arcuate projections alternating with the recesses, such that the recesses provide venting passages extending between the front and back faces when the member is a close fit in said circular aperture, and wherein, at the front fiat face of the block each recess is arcuate and has a radial dimension less than a minimum arcuately measured dimension of the recess; and a central part of a radially inner surface of each recess extends from the back flat face towards the front flat face at an inclination away from the axis of the block and from a minimal radial dimension at a junction of said central part with the back flat face.

2. A venting member as claimed in claim 1, wherein a plurality of slots opens into said front fiat face, said slots also extend from the central parts of the radially inner surfaces of the recesses towards an axial region of the block, and at least one of said slots so extends from each said radially inner surface.

3. A venting member as claimed in claim 1, wherein, radially outer surfaces of the projections are portions of a screw thread which is interrupted by the recesses, and the radial dimensions of said outer surfaces of the projections progressively decrease from said front face towards said back face.

References Cited UNITED STATES PATENTS 4/1941 Rienacker 164-410 6/1965 McIntyre 164234 X US. Cl. X.R. 

